1. Field of the Invention
This invention relates to blow forming mechanisms for mass production of double-walled bodies and, more particularly, to a novel blow forming apparatus in which a parison is extruded or injected into a blowing mold in the form of coaxial parison, defining the double walls of the body.
2. Description of the Prior Art
In the past, it has been conventional practice to employ blow mold techniques and procedures for forming single-walled bodies or containers such as pill bottles, cosmetic containers, liquid storage bottles and the like. In this practice, it is the usual procedure to either inject or extrude a parison into a defined cavity followed by introduction of high pressure air which forces the parison against the shaped walls of the cavity. Upon removal of the mold from around the blown part, the part is then separated from the mold and another part commences formation. Other methods may also be employed for producing single walled vessels or containers. However, it has heretofore been unknown to automatically produce double walled containers on a mass production basis wherein the double walls merge at their opposite ends into an integral sealing and joining formation. It is known that double-walled vessels can be fabricated by using separately produced inner and outer vessels which are inserted within one another and held in place by support pieces such as collars, couplings and the like. Solvent application, ultra sonic or heat-sealing at the junction of the two vessels provides a single air and/or vacuum trapped double walled vessel. An example of this prior art double-walled vessel may be a conventional vacuum bottle or thermos bottle.
Another disadvantage of conventional single-walled vessel production apparatus resides in the necessity of moving the partially formed part from one place to another or from one station to another so that different phases of the formation can be completed. In other words, means are not provided whereby the parison may be completely formed and shaped at one station in the machine operation. The partially shaped parison must be moved from one portion of the mold to another portion in order to successively shape the whole parison into a desired configuration. This problem again makes the formation of double-walled vessels impossible if not extremely difficult when employing conventional molding machines.
Therefore, a need has long existed to provide a suitable apparatus for producing double-walled vessels by either injection-blow-molding techniques or by employing extrusion-blow molding practices.